P971: EFFECT OF DARATUMUMAB ON STEM CELL YIELDS IN PATIENTS WITH NEWLY DIAGNOSED MULTIPLE MYELOMA: REPORT FROM THE MULTIPLE MYELOMA LAZIO GROUP.
Authors: Francesca Fazio, Mauro Passucci, Chiara Lisi, Jacopo Micozzi, Luana Fianchi, Francesca DI Landro, Tommaso Za, Svitlana Gumenyuk, Silvia Ferraro, Barbara Anaclerico, Laura De Padue, Ombretta Annibali, Angela Rago, Alfonso Piciocchi, Velia Bongarzoni, Luca Cupelli, Andrea Mengarelli, Valerio De Stefano, Maurizio Martelli, Maria-Teresa Petrucci
Journal: HemaSphere (2023)

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: High dose chemotherapy followed by autologous stem cell transplantation (ASCT) is the standard of care therapy for newly diagnosed multiple myeloma (NDMM) patients (pts). The anti-CD38 IgG1-k monoclonal antibody daratumumab (dara) demonstrated to improve depth and duration of response in transplant eligible MM pts when added to the standard of care induction regimen. Recent studies have indicated a potential reduction in stem cell yields in MM pts exposed to dara prior to stem cell mobilization [1]. Aims: The primary endpoint of this study is to investigate the possible impact of dara on stem cell yields with mobilization therapy and to identify possible features that affect stem cell yields. Methods: We retrospectively evaluated 51 pts with NDMM managed at 8 Italian Hematology Centers who underwent induction therapy based on dara-bortezomib, thalidomide and dexamethasone (D-VTD) between November 2021 and July 2022. Following induction therapy, pts underwent mobilization therapy as per institutional guidelines. Results: Fifty-one pts were included in the analysis. The median age was 60 (range: 54-64); 65% were male; 49% of pts were stage I, and 37% were stage II, according to the International Staging System (ISS) and the Revised- ISS, respectively. Forty-eight pts (94%) received 4 cycles of D-VTD as induction therapy after mobilization therapy. The baseline clinical characteristics and the frontline induction therapy were summarized in Table 1. Globally, 48 out of 51 pts (94%) analyzed, met the collection goal after mobilization therapy, however, for 3 pts (6%) a second mobilization attempt was required. In addition, for another 3 pts (6%) a third mobilization attempt was needed. In the majority of pts (92%), a combination of cyclophosphamide with granulocyte colony stimulating factor was used as the first mobilizing regimen attempt. Plerixafor on demand was administered during stem cell mobilization in 15/51 pts (32%) failing to achieve the desired collection goals, confirming that a higher use of plerixafor was necessary in the dara-based induction therapy, as previously reported1. Specifically, 14 out of 15 pts (99%) met the collection goal at the first mobilization therapy attempt receiving plerixafor on demand, and most of these pts (71%) received only one dose of plerixafor. The majority of the pts who did not meet the goal in one apheresis procedure were able to meet the goal with 1 (64%) or 2 (10%) additional procedures. The median number of CD34+ stem cells collection yield was 8 x 106 cells/Kg (range: 1.4-16). The median time between the last day of induction therapy and the first day of mobilization therapy was 31 days (range: 25-45). Univariate analysis showed that a higher level of baseline LDH was associated with a lower rate of collection goal, after the first mobilization attempt (p=0.017). Pts with a median lower pre-mobilization therapy level of neutrophils and platelets showed a significantly lower rate of collection goal after the first mobilization attempt (p=0.013 and p=0.035, respectively), possibly due to prolonged hematological toxicity after induction therapy. Summary/Conclusion: On introducing dara to the induction treatment, we observed that a higher use of plerixafor and more days of apheresis procedures are required to meet the collection goal at the first mobilization attempt. A larger cohort of pts are needed to confirm our preliminary results and to evaluate a new mobilization therapy schedule to guarantee adequate stem cell yields. 1] Hulin C et al. Haematologica 2021Keywords: Multiple myeloma, Immune therapy